WO2018143294A1

WO2018143294A1 - Energy conversion film and energy conversion element using same

Info

Publication number: WO2018143294A1
Application number: PCT/JP2018/003271
Authority: WO
Inventors: 小池　弘; 祐太郎菅俣; 誠一郎飯田
Original assignee: 株式会社ユポ・コーポレーション
Priority date: 2017-02-01
Filing date: 2018-01-31
Publication date: 2018-08-09
Also published as: CN110214358A; JPWO2018143294A1; CA3051662A1; EP3579258A1; EP3579258A4; US20190393806A1; JP6771591B2; CN110214358B; US11515810B2

Abstract

Provided are: an energy conversion film which exhibits excellent charge-holding performance and in which deterioration of the piezoelectric performance is suppressed even when the film is exposed to a high-temperature environment; and an energy conversion element or the like using said energy conversion film. The energy conversion element is characterized by being provided with: an energy conversion film which includes at least a charged resin film formed of a resin film including at least a thermoplastic resin and a metal soap; and an electrode provided on at least one surface of the energy conversion film.

Description

Energy conversion film and energy conversion element using the same

The present invention is an electrical-mechanical energy conversion that converts mechanical energy such as vibration and pressure changes into electrical energy, an electrical-thermal energy conversion that converts thermal energy such as infrared rays and temperature changes into electrical energy, and mechanical energy into thermal energy. The present invention relates to an energy conversion film that can be used for mechanical-thermal energy conversion and the like, and an energy conversion element using the same. The energy conversion film of the present invention is an electret having excellent heat resistance and excellent electro-mechanical energy conversion performance.

An electret is a polymer material that forms an electric field to the outside (which exerts an electric force) by semipermanently holding the electric polarization inside even when there is no electric field outside, and is inherently difficult to conduct electricity. In addition, it is a material in which a part of the material is semipermanently polarized (macroscopically charged, holding electric charges) by thermally or electrically treating inorganic materials or the like.
Conventionally, electrets made of a polymer material are used in various forms such as a film, a sheet, a fiber, a woven fabric, and a non-woven fabric, depending on the use mode. In particular, electret filters formed by molding electrets made of polymer materials have been widely used in applications such as air filters that efficiently adsorb minute dust, allergens, and the like by an electric field. In addition, electrets made of polymer materials are widely used in various applications as materials for electro-mechanical energy conversion such as speakers, headphones, microphones, ultrasonic sensors, pressure sensors, acceleration sensors, vibration control devices, and the like.

Also, electrets using a porous resin film are known to exhibit a piezoelectric effect, and can be used for sound detection, sound generation, vibration measurement, vibration control, and the like. For example, a foamed film is proposed in which a foamable thermoplastic resin is extruded into a film and foamed at the same time to obtain a porous film having a large number of internal pores, and then the film is stretched two-dimensionally. (Patent Document 1).

However, when such a foamed film is exposed over time or under reduced pressure, the gas gradually escapes from the internal pores and becomes deflated, so that a certain pore shape, expansion ratio, and porosity are maintained. Is difficult. Therefore, Patent Document 1 discloses a method in which heat treatment is performed at the stage where the foamed film is expanded, and the shape is fixed by promoting crystallization of the thermoplastic resin. However, if the heat treatment is performed at a temperature higher than the phase transition temperature or glass transition temperature of the thermoplastic resin, the gas permeability of the thermoplastic resin is increased, so that the gas easily escapes from the internal pores of the foamed film. However, there is a drawback that the piezoelectric performance deteriorates.

On the other hand, the present inventors use a thermoplastic resin and an inorganic fine powder or organic filler having a specific volume average particle size as a piezoelectric material having high energy conversion performance, and a film for energy conversion having a certain pore size. (Patent Document 2 and Patent Document 3).

However, when these conventional energy conversion films are used in a high temperature environment such as an engine room of a car, they are exposed to a temperature higher than the phase transition temperature or glass transition temperature of the thermoplastic resin used in the film. there is a possibility. When the conventional energy conversion film is stored or used for a long period of time in such a high temperature environment, there is a drawback that the charge holding performance is lowered and the piezoelectric performance is lowered.

On the other hand, there is an electret sheet in which a positively chargeable charge control agent such as a specific azine derivative or a quaternary ammonium salt compound and a negatively chargeable charge control agent such as a specific salicylic acid derivative metal salt or an azochrome compound are used in combination. (Patent Document 4). According to the electret sheet of Patent Document 4, it is said that excellent piezoelectric performance can be maintained even under high temperature conditions by containing the above-described charge control agent as an additive in the resin film.

JP-A-61-148044 JP 2011-084735 A JP 2011-086924 A JP 2014-074104 A

The present inventors studied application of the technology of Patent Document 4 to an energy conversion film and an energy conversion element. However, the charge control agent described in Patent Document 4 has insufficient heat resistance, and the energy conversion film and the energy conversion element using this charge control agent still have insufficient piezoelectric performance in a high temperature environment. It has been found. Therefore, in order to enhance the piezoelectric performance in a high temperature environment, there is a demand for an additive used for an energy conversion film that enhances charging properties and has heat resistance.

The present invention has been made in view of such background art. An object of the present invention is to provide an energy conversion film, an energy conversion element using the same, and the like that are excellent in charge retention performance and suppressed in deterioration of piezoelectric performance even when exposed to a high temperature environment.

Note that the present invention is not limited to the purpose described here, and is an operational effect derived from each configuration shown in the embodiment for carrying out the invention described later, and can also exhibit an operational effect that cannot be obtained by the conventional technology. It can be positioned as another purpose.

As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention have excellent charge retention performance even when a specific energy conversion film is exposed to a high temperature environment. As a result, the inventors have found that the decrease in the thickness is suppressed, and have completed the present invention.

That is, the present invention provides various specific modes shown below.
[1] An energy conversion film including at least a charged resin film made of a resin film containing at least a thermoplastic resin and a metal soap, and an electrode provided on at least one surface of the energy conversion film, Energy conversion element.
[2] The energy conversion element according to [1], wherein the thermoplastic resin contains a polyolefin resin, and the metal soap has a melting point of 50 ° C. to 220 ° C.
[3] The energy conversion element according to [1] or [2], wherein the metal soap is a salt of a fatty acid having 5 to 30 carbon atoms and a metal.
[4] The energy conversion according to any one of [1] to [3], wherein the metal soap is a salt of a fatty acid and a metal belonging to Group 2 to Group 13 of the periodic table. element.
[5] The energy conversion element according to [3] or [4], wherein the metal is at least one selected from the group consisting of zinc, calcium, and aluminum.

[6] The energy conversion element according to any one of [1] to [5], wherein the resin film is a porous resin film having pores therein.
[7] The energy according to any one of [1] to [6], wherein the energy conversion film includes at least a charged resin film in which charges are injected into the resin film by a direct current corona discharge treatment. Conversion element.
[8] The energy according to any one of [1] to [7], wherein the electrode has a surface resistivity of 1 × 10 ⁻³ Ω / □ to 9 × 10 ⁷ Ω / □. Conversion element.
[9] After heat-treating the energy conversion element at 85 ° C. for 14 days, the energy conversion element was left standing on a horizontal surface at a temperature of 23 ° C. and a relative humidity of 50%, and a diameter of 9.5 mm from a height of 8 mm in the vertical direction. The energy conversion element according to any one of [1] to [8], wherein a maximum voltage generated by an impact when a 3.5 g iron ball is naturally dropped is 5 mV or more .
[10] An energy conversion film comprising at least a charged resin film made of a resin film containing at least a thermoplastic resin and a metal soap. Here, it is preferable that the energy conversion film further includes at least one of the technical features of [2] to [9].

The energy conversion film of the present invention and the energy conversion element using the same have a metal soap in the film, so that the charge retention performance is enhanced, and the piezoelectric performance is hardly degraded even when exposed to a high temperature environment. Therefore, speakers, headphones, ultrasonic transducers, ultrasonic motors, vibration control devices, microphones, ultrasonic sensors, pressure sensors, acceleration sensors, strain sensors, fatigue / It is particularly useful as a module member used in crack sensors, medical sensors, measuring instruments, control devices, abnormality diagnosis systems, security devices, stabilizers, robots, percussion instruments, game machines, power generation devices and the like.

It is a schematic sectional drawing which shows the one aspect | mode of the energy conversion film 1 of this invention. It is a schematic sectional drawing which shows the one aspect | mode of the energy conversion element 5 of this invention. It is a schematic diagram which shows an example of an electretization apparatus. It is a schematic diagram which shows the falling ball test apparatus used by the test example of this invention.

Hereinafter, each embodiment of the present invention will be described with reference to the drawings. The following embodiments are examples for explaining the present invention, and the present invention is not limited only to the embodiments. In the following, unless otherwise specified, positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios. In the present specification, for example, the description of a numerical range of “1 to 100” includes both the lower limit value “1” and the upper limit value “100”. This also applies to other numerical range notations.

The energy conversion film of the present invention includes at least a charged resin film made of a resin film containing at least a thermoplastic resin and a metal soap. Here, the charged resin film is one in which electric charge is injected into the resin film. That is, the energy conversion film and the charged resin film in the present invention are the “charged” resin film, in which charges are intentionally injected into the resin film, and a larger amount than the resin film. Charged. Moreover, the energy conversion element of this invention provides the electrode in the at least one surface of this energy conversion film. Hereinafter, each member which comprises the energy conversion film of this invention and the energy conversion element using the same, and its manufacturing method are explained in full detail.

1 and 2 show preferred embodiments of the energy conversion film and the energy conversion element of the present invention. The energy conversion film 1 includes a charged resin film in which charges are injected into a resin film 2 (core layer) containing at least a thermoplastic resin and metal soap, and

skin layers

3 and 4 are provided on both front and back surfaces of the resin film 2 as necessary. (Resin film containing at least a thermoplastic resin) is provided. The energy conversion element 5 is configured by providing

electrodes

6 and 7 on at least one surface of the energy conversion film 1.

[Energy conversion film]
The energy conversion film (charged resin film) of the present invention can be obtained by injecting a charge into a resin film containing a thermoplastic resin and metal soap and charging it. Here, the resin film into which charges are injected is preferably a porous resin film having a large number of pores (hereinafter also referred to as “internal pores”).

In addition, regarding the energy conversion film of the present invention, the one before electretization treatment (uncharged) described later in this specification is referred to as “resin film” or “porous resin film”, and after electretization treatment. The one (charged one) is referred to as “energy conversion film”, “charged resin film” or “charged porous resin film”. In the energy conversion film of the present invention, the electro-mechanical energy conversion performance includes not only the ability to convert mechanical energy (kinetic energy) into electrical energy, but also the ability to convert electrical energy into mechanical energy (kinetic energy). Including.

[Resin film]
The resin film is obtained by molding a resin composition containing at least a thermoplastic resin described later and a metal soap described later into a thin film by a molding method described later. The resin film is preferably a porous resin film having a large number of pores inside. Moreover, it is preferable that a resin film is a multilayer resin film (laminated resin film) containing a core layer and a skin layer.

Furthermore, in order to improve the adhesion with the electrode provided for constituting the energy conversion element, the surface of the resin film may be subjected to a surface treatment described later, and an anchor coat layer is provided on the surface of the resin film. May be. The energy conversion element having an anchor coat layer has a laminated structure of energy conversion film / anchor coat layer / electrode.

[Porous resin film]
The porous resin film contains at least a thermoplastic resin and a metal soap, preferably a resin composition further containing a pore-forming nucleating agent, which will be described later, and is formed into a thin film by a molding method described later. A hole is formed.

The porous resin film is preferably a multilayer resin film having a core layer and a skin layer, and has a skin layer made of a stretched resin film on at least one side of a core layer made of a stretched resin film having pores therein. A multilayer resin film is more preferable, and a multilayer resin film having skin layers made of a stretched resin film on both surfaces of a core layer made of a stretched resin film having pores therein is more preferred. In addition, the porous resin film has a non-reactive gas infiltrated into the resin film under pressure, then opened under non-pressurization to cause gas foaming to moderate the porosity, and then under non-pressure. Heat treatment may be performed to fix the pores.

When the porous resin film includes a stretched resin film having pores therein as in the core layer, the stretched resin film contains at least a thermoplastic resin, a metal soap, and a pore-forming nucleating agent. Is preferably formed by stretching pores under a temperature condition equal to or lower than the melting point of the thermoplastic resin.

In the porous resin film, pores having a shape suitable for accumulating electric charges inside and a shape that provides high compression recovery to the porous resin film can be formed.

The shape and size of the pores of the porous resin film may be appropriately set according to the required performance and the like, and are not particularly limited. In the energy conversion film, it is considered that different charges are held in pairs on the inner surfaces of the individual pores inside the porous resin film, like a capacitor. For this reason, the pores of the porous resin film require a certain area and height as in the case of the single plate capacitor in order to accumulate electric charges therein. If there is no area above a certain level, sufficient electrostatic capacity cannot be obtained, and it is difficult to obtain an electret with excellent performance. Further, if there is no height (distance) above a certain level, discharge (short circuit) occurs inside the hole, and it is difficult to accumulate charges. On the other hand, if the height (distance) is too large, it is disadvantageous for polarization of charges, and it is difficult to obtain an electret with excellent stability. Therefore, it was considered that the larger the size (area) of the individual pores inside the porous resin film, the more effectively it functions. However, if the size of the vacancies is excessively large, adjacent vacancies communicate with each other, and a discharge (short circuit) occurs between adjacent vacancies, making it difficult to accumulate charges.

From these viewpoints, the porous resin film preferably has a specific amount of pores of a specific size (effective for charge accumulation) from the viewpoint of stably storing more charges. On the observation image when the film is observed in an arbitrary cross section, there are 100 holes having a height of 3 to 30 μm in the thickness direction of the film and a diameter of 50 to 500 μm in the surface direction of the film. / Mm ² or more, preferably 150 pieces / mm ² or more, more preferably 200 pieces / mm ² or more, and particularly preferably 300 pieces / mm ² or more. On the other hand, from the viewpoint of short-circuit suppression between adjacent holes and the strength of the substrate, holes having a height of 3 to 30 μm in the thickness direction of the film and a diameter of 50 to 500 μm in the surface direction of the film are provided. 3,000 / mm ² or less, preferably 2,500 / mm ² or less, more preferably 2,000 / mm ² or less, more preferably 1,500 / mm ² or less. It is particularly preferable to have it. As the number of effective vacancies in the porous resin film increases, the charge storage capacity tends to improve and the energy conversion efficiency tends to improve, but if the number of vacancy of a certain size in the film increases too much In addition, there is an increased possibility that adjacent holes communicate with each other and discharge (short circuit) occurs between adjacent holes, and further, the strength of the film itself is reduced and the restoring force against external stress such as compression is reduced. There is a tendency. Insufficient compression recovery results in adverse effects such as a decrease in the recovery rate during repeated compression and decompression, so when used as a piezoelectric element that converts mechanical energy into electrical energy, the product life Inconveniences such as shortening of life may occur. Therefore, it is preferable to adjust the shape and size of the pores of the porous resin film in consideration of these balances.

The porous resin film is obtained by, for example, melting and kneading a resin composition containing a pore-forming nucleating agent in a thermoplastic resin, which is a polymer material having excellent insulating properties, to form a sheet, and then heating the resin composition. By forming the pores with the pore-forming nucleating agent as the starting point (core) inside the film by stretching at a temperature higher than the glass transition point of the plastic resin and lower than the melting point of the thermoplastic resin, Obtainable.

The porosity of such a porous resin film may be appropriately set according to required performance and the like, and is not particularly limited, but is preferably 20 to 80%. Such a porosity is correlated with the number of effective holes. In addition, the porosity of a porous resin film means the ratio (volume ratio) of the volume which the void | hole in the same material occupies with respect to the total volume of the whole same material. The porosity of the porous resin film is equal to the ratio (area ratio) of the area occupied by the pores to the cross section of the same material on the assumption that the pores are uniformly distributed throughout the same material.

Therefore, the porosity of the porous resin film is determined by observing the cross-section of the same material with a scanning electron microscope, capturing the observation image in an image analysis device, and analyzing the image of the observation area to determine the area ratio of the pores on the cross-section. It can be obtained as a value obtained by calculation. Specifically, a sample for cross-sectional observation is created so that the pores are not crushed by a technique such as a gallium focused ion beam from a porous resin film or an energy conversion film, and a scanning electron microscope (manufactured by JEOL Ltd., Using a product name: JSM-6490) or the like, cross-sectional observation of the sample obtained at an appropriate magnification (for example, 2000 times) is performed, and the observation area of the obtained cross-sectional photograph is image analysis apparatus (manufactured by Nireco Corporation) , Trade name: LUZEX AP) or the like can be used to calculate the ratio (area ratio) of the area occupied by the vacancies in the sample cross section, and this can be used as the vacancy ratio.

On the other hand, when the raw material used for the porous resin film is known or a resin composition in which no pores are formed is available, the porosity of the porous resin film is calculated based on the following formula 1. Can also be calculated.

From the viewpoint of providing a large number of pores of a size suitable for accumulating charges inside the film and ensuring the charge accumulation capacity, the porosity of the porous resin film is preferably 20% or more, 25 % Or more, more preferably 30% or more, and particularly preferably 35% or more. On the other hand, it is possible to suppress the short circuit of the charge due to the communication of the pores, the extremely low elastic modulus of the porous resin film, the decrease in the restoring property in the thickness direction, and the suppression of the poor durability. Therefore, the porosity of the porous resin film is preferably 80% or less, more preferably 70% or less, further preferably 60% or less, and particularly preferably 55% or less.

Hereinafter, the resin film or the porous resin film may be generally referred to as “resin film”. The thickness of the porous resin film is preferably in the same range as the thickness of the resin film.

[Raw material of porous resin film]
The porous resin film constituting the energy conversion film preferably contains a pore-forming nucleating agent in addition to the thermoplastic resin and the metal soap. Specifically, based on the total mass of the single-layer porous resin film (hereinafter sometimes referred to as “single-layer film standard”), the thermoplastic resin is 50 to 98 mass% and the metal soap is 0.02 mass. % To 20% by mass, preferably 1.98 to 49.98% by mass of a pore-forming nucleating agent, 60 to 97% by mass of a thermoplastic resin, 0.03% to 10% by mass of a metal soap, More preferably, it contains 2.97 to 39.97% by mass of a pore-forming nucleating agent, 65 to 96% by mass of a thermoplastic resin, 0.05% to 5% by mass of a metal soap, and a pore-forming nucleating agent. Is more preferably 3.95 to 34.95% by mass, thermoplastic resin is 70 to 85% by mass, metal soap is 0.1% by mass to 3% by mass, and pore-forming nucleating agent is 14.9 to Most preferably, it contains 29.9% by weight. In addition, when the single layer porous resin film includes other components described later in addition to the three components of the thermoplastic resin, the metal soap, and the pore-forming nucleating agent, the total content of the three components is less than 100%. It may be.

Moreover, when an energy conversion film is provided with the laminated structure which has a core layer, a skin layer, etc. so that it may mention later, on the basis of the total mass of the laminated structure (it may be called "laminated film reference | standard" hereafter). Further, it preferably contains 50 to 98% by mass of thermoplastic resin, 0.02% to 20% by mass of metal soap, 1.98 to 49.98% by mass of a pore-forming nucleating agent, and 60% of thermoplastic resin. More preferably, it contains ~ 97% by mass, metal soap is 0.03% by mass to 10% by mass, pore-forming nucleating agent is 2.97 to 39.97% by mass, thermoplastic resin is 65 to 96% by mass, More preferably, it contains 0.05% to 5% by weight of metal soap, 3.95 to 34.95% by weight of a pore-forming nucleating agent, 70 to 85% by weight of thermoplastic resin, and 0.8% of metal soap. 1% to 3% by mass, pore formation Agent most preferably contains 14.9 to 29.9 wt%. In addition, when the laminated film includes other materials described later in addition to the three components of the thermoplastic resin, the metal soap, and the pore forming nucleating agent, the total content of the three components may be less than 100%.

[Thermoplastic resin]
The thermoplastic resin used for the resin film is a matrix resin that forms the resin film itself, and imparts a piezoelectric effect and restorability to the energy conversion film. The thermoplastic resin suitable for use as an energy conversion film is preferably an insulating polymer material that is difficult to conduct electricity. For example, polyolefin resins such as high-density polyethylene, medium-density polyethylene, low-density polyethylene-containing ethylene resins, propylene resins, polymethyl-1-pentene, and cyclic polyolefins; ethylene / vinyl acetate copolymers, ethylene / acrylic acid copolymers Polymers, functional group-containing polyolefin resins such as maleic acid-modified polyethylene and maleic acid-modified polypropylene; polyamide resins such as nylon-6 and nylon-6,6; polyethylene terephthalate and copolymers thereof, polybutylene terephthalate, polybutylene Polyester resins such as succinate and polylactic acid; polycarbonate, atactic polystyrene, syndiotactic polystyrene and the like are exemplified, but not limited thereto. Among these thermoplastic resins, polyolefin resins and functional group-containing polyolefin resins having low hygroscopicity and high insulation properties are preferably used, and polyolefin resins are more preferably used. A thermoplastic resin can be used individually by 1 type or in combination of 2 or more types.

Examples of polyolefin resins include olefins such as ethylene, propylene, butene, pentene, hexene, octene, butylene, butadiene, isoprene, chloroprene, methylpentene, cyclobutenes, cyclopentenes, cyclohexenes, norbornenes, and tricyclo-3-decenes. Homopolymers of these types, and copolymers composed of two or more types of these olefins, but are not particularly limited thereto. Specific examples of polyolefin resins include high density polyethylene, medium density polyethylene, propylene resins, copolymers of ethylene and other olefins, copolymers of propylene and other olefins, and the like. However, it is not particularly limited to these.

Among these polyolefin resins, ethylene resins and propylene resins are preferable, isotactic or syndiotactic and propylene homopolymers having various degrees of stereoregularity, or propylene as a main component, and ethylene and Propylene resin containing a propylene copolymer copolymerized with α-olefin such as 1-butene, 1-hexene, 1-heptene, 4-methyl-1-pentene, etc. is non-hygroscopic and insulating. In addition, it is more preferable from the viewpoint of chargeability, workability, Young's modulus, durability, cost, and the like. The propylene copolymer may be a binary system or a ternary or higher multi-element system, and may be a random copolymer or a block copolymer.

Further, specific examples of the functional group-containing polyolefin resin include a copolymer with a functional group-containing monomer copolymerizable with the olefins. Examples of functional group-containing monomers include styrenes such as styrene and α-methylstyrene; vinyl acetate, vinyl alcohol, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl caproate, vinyl laurate, vinyl stearate, vinyl benzoate. , Carboxylic acid vinyl esters such as vinyl butylbenzoate and vinyl cyclohexanecarboxylate; (meth) acrylic acid; methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, octyl ( (Meth) acrylate, 2-ethylhexyl (meth) acrylate, stearyl (meth) acrylate, benzyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) Acrylic esters such as acrylate, (meth) acrylamide, N-metalol (meth) acrylamide; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, cyclopentyl vinyl ether, cyclohexyl vinyl ether, benzyl vinyl ether, and phenyl vinyl ether Although it is mentioned, it is not specifically limited to these. From these functional group-containing monomers, one or two or more types appropriately selected and polymerized can be used as necessary.

Furthermore, it is also possible to use those polyolefin-based resins and functional group-containing polyolefin-based resins that are graft-modified as necessary. A known technique can be used for graft modification, and specific examples include graft modification with an unsaturated carboxylic acid or a derivative thereof. Examples of the unsaturated carboxylic acid include (meth) acrylic acid, maleic acid, fumaric acid, itaconic acid and the like. As the derivative of the unsaturated carboxylic acid, an acid anhydride, ester, amide, imide, metal salt or the like can be used. Specifically, maleic anhydride, itaconic anhydride, citraconic anhydride, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, glycidyl (meth) acrylate, monoethyl maleate, Maleic acid diethyl ester, fumaric acid monomethyl ester, fumaric acid dimethyl ester, itaconic acid monomethyl ester, itaconic acid diethyl ester, (meth) acrylamide, maleic acid monoamide, maleic acid diamide, maleic acid-N-monoethylamide, maleic acid- N, N-diethylamide, maleic acid-N-monobutylamide, maleic acid-N, N-dibutylamide, fumaric acid monoamide, fumaric acid diamide, fumaric acid-N-monoethylamide, fumaric acid-N, N-diethylamide , Fumaric acid-N-mono Chiruamido, fumaric acid -N, N- dibutylamide, maleimide, N- butyl maleimide, N- phenylmaleimide, (meth) sodium acrylate, there may be mentioned (meth) potassium acrylate is not particularly limited thereto.

As the graft modified product, the graft monomer is generally graft modified by adding 0.005 to 10% by mass, preferably 0.01 to 5% by mass, based on at least one of the polyolefin resin and the functional group-containing polyolefin resin. Things.

As a thermoplastic resin suitable for use in the porous resin film, one of the above thermoplastic resins may be selected and used alone, or two or more may be selected and used in combination. May be.

The content (content rate) of the thermoplastic resin in the resin film is not particularly limited. For example, a sufficient pore interface is formed in the film as a matrix resin of the porous resin film, and communication between the pores is suppressed. From the standpoint of ensuring the mechanical strength of the porous resin film, it may be set as appropriate. Specifically, the thermoplastic resin is preferably contained in an amount of 50% by mass or more, more preferably 60% by mass or more, further preferably 65% by mass or more, and more preferably 70% by mass based on the total mass of the resin film. It is particularly preferable to include the above. On the other hand, it is preferable to contain 98% by mass or less of the thermoplastic resin, more preferably 97% by mass or less, still more preferably 96% by mass or less, and particularly preferably 85% by mass or less.

[Metal soap]
Conventionally, when the resin film contains metal soap, it has been considered that the resin film has a higher dielectric constant and lowers charge retention performance and lowers heat resistance as compared with the case of containing a charge control agent. However, as a result of studies by the present inventors, it has been found that when metal soap is included, it has the same level of chargeability as a charge control agent and is excellent in heat resistance. In other words, the resin film contains metal soap, so that the charge retention performance of the resin film is enhanced, and the energy conversion film obtained by electretizing it has its piezoelectric performance even when stored and used in a high temperature environment. Becomes difficult to decrease.

As a metal soap suitable for use as an energy conversion film, it is melted and uniformly dispersed in a thermoplastic resin in the kneading stage of the resin film raw material, and the environment temperature of the energy conversion film and the energy conversion element using the energy conversion film In addition, those that are solid at the storage temperature are preferably used because they easily exhibit high charge retention performance. Therefore, the melting point of the metal soap is preferably in the range of 50 ° C. or more and 50 ° C. or more higher than the melting point of the thermoplastic resin, and 70 ° C. or more and 40 ° C. or less higher than the melting point of the thermoplastic resin. It is more preferable to be within the range, and it is further preferable to be within a range of 100 ° C. or higher and 30 ° C. or higher than the melting point of the thermoplastic resin. For example, when a polypropylene resin (melting point: 160 to 170 ° C.) is used as the thermoplastic resin, it is preferable to use a metal soap having a melting point of 50 ° C. to 220 ° C., and a metal soap having a melting point of 70 ° C. to 210 ° C. It is more preferable to use a metal soap having a melting point of 100 ° C. to 200 ° C.

Since the metal soap has a melting point within the above-mentioned preferred temperature range, it is melted and uniformly dispersed in the thermoplastic resin during the production of the resin film, and the dispersion state is maintained in the thermoplastic resin after the resin film is formed. It solidifies as it is and is difficult to flow. At the time of electret treatment, it is presumed that the metal soap is oriented by the dipoles in the molecule, and the charge retention performance of the energy conversion film is enhanced by the orientation of the metal soap.

The metal soap is preferably a metal salt of a fatty acid, and more preferably a metal salt of a higher fatty acid. Here, as the fatty acid, saturated fatty acid and unsaturated fatty acid having 5 to 30 carbon atoms, preferably 6 to 28 carbon atoms, more preferably 8 to 24 carbon atoms, and further preferably 10 to 20 carbon atoms, and These structural isomers are mentioned. In addition, these carbon numbers show the quantity per molecule of fatty acid.

Specific examples of saturated fatty acids include pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, and 12-hydroxyoctadecane Examples include acid, icosanoic acid, docosanoic acid, tetracosanoic acid, hexacosanoic acid, and octacosanoic acid, but are not particularly limited thereto.

Specific examples of unsaturated fatty acids include trans-2-butenoic acid, 9-tetradecenoic acid, 9-hexadecenoic acid, cis-6-hexadecenoic acid, cis-9-octadecenoic acid, trans-9-octadecenoic acid, cis -9-icosenoic acid, cis-13-docosenoic acid, cis-15-tetracosenoic acid, cis, cis-9,12-octadecadienoic acid, 9,11,13-octadecatrienoic acid, cis, cis, cis- 9,12,15-octadecatrienoic acid, cis, cis, cis-8,11,14-icosatrienoic acid, 6,9,12,15-octadecatetraenoic acid, 5,8,10,12,14- Examples thereof include octadecapentaenoic acid, 4,7,10,13,16,19-docosahexaenoic acid, but are not particularly limited thereto.

Among these fatty acids, the saturated fatty acid metal salt tends to have a high melting point, and it is easy to obtain an energy conversion film with improved heat resistance. Therefore, it is preferable to use a saturated fatty acid.

The metal element of the metal soap is not particularly limited as long as it is a metal that forms a stable salt with a fatty acid. However, from the viewpoint of the melting point and charge retention performance of the obtained metal soap, it is usually monovalent, divalent, or trivalent. It is preferable to use at least one metal element belonging to Group 1 to Group 13 of the Periodic Table (old group number belonging to Group IA to Group IIIB), which is a divalent or trivalent metal. It is more preferable to use at least one metal element belonging to Group 2 to Group 13 of the periodic table (old group number belonging to Group IIA to Group IIIB). It is more preferable to use at least one metal element of Group 13 (old group number IIA, IIB and IIIB). More specifically, at least one of sodium (Group 1), magnesium (Group 2), calcium (Group 2), barium (Group 2), zinc (Group 12) and aluminum (Group 13). In particular, from the viewpoint of safety, it is particularly preferable to use at least one of calcium, zinc and aluminum, and from the viewpoint of further improving the charge retention performance, it is particularly preferable to use calcium or aluminum. Most preferably, aluminum is used. The metal soap may be a basic salt.

The metal soap most preferably used in the energy conversion film of the present invention is a saturated higher fatty acid aluminum salt. Specific examples of the saturated higher fatty acid aluminum salt include dihydroxyaluminum octadecanoate, hydroxyaluminum dioctadecanoate, aluminum trioctadecanoate, dihydroxyaluminum dodecanoate, hydroxyaluminum dododecanoate, aluminum tridodecanoate, and dihydroxyaluminum 2-ethylhexanoate. , Hydroxy aluminum di-2-ethylhexanoate, aluminum tri-2-ethylhexanoate and the like, but are not particularly limited thereto.

The metal soaps as described above are generally used as various additives (for example, stabilizers, lubricants, filler dispersants, anti-spot agents, fluidity improvers, nucleating agents, or antiblocking agents) in the plastics industry. Has been. However, the metal soap in the energy conversion film of the present invention is added to increase the chargeability of the film, and is added as a functional agent that suppresses the deterioration of the piezoelectric performance of the conventional energy conversion film in a high temperature environment. To do. Therefore, in the present invention that suppresses the deterioration of the piezoelectric performance of the energy conversion element, the amount is relatively larger than the blending amount (for example, 0.01% by mass) when used as the above-described conventional general various additives. It is preferable to add a metal soap.

The content of the metal soap in the resin film is based on 100% by mass of the composition comprising the thermoplastic resin and the metal soap constituting the single-layer resin film (hereinafter referred to as “composition standard” of the single-layer resin film and From the viewpoint of charge retention ability, it is preferably 0.02% by mass or more, more preferably 0.03% by mass or more, further preferably 0.05% by mass or more. The content is particularly preferably 1% by mass or more, and most preferably 0.2% by mass or more.

In addition, the metal soap has a peak effect even if added excessively with respect to 100% by mass of the composition comprising the thermoplastic resin and the metal soap constituting the single-layer resin film, and adverse effects such as bleed out are increased. , Preferably 20% by mass or less, preferably 10% by mass with respect to 100% by mass of the composition comprising the thermoplastic resin and the metal soap (hereinafter, sometimes referred to as “composition standard” of the single-layer resin film). %, More preferably 5% by mass or less, still more preferably 3% by mass or less, and most preferably 0.7% by mass or less.

[Void-forming nucleating agent]
The pore-forming nucleating agent used for the porous resin film is added to form pores in the film using this as a nucleus. Examples of the pore-forming nucleating agent suitable for use in the porous resin film include inorganic fine powders and organic fillers. By the addition of these pore-forming nucleating agents and the stretching step described later, it becomes possible to form pores in the film. It is possible to control the frequency of pores by controlling the content of the pore-forming nucleating agent, and by controlling the particle size of the pore-forming nucleating agent, the size of the pores (high And the diameter) can be controlled.

When the resin film contains a pore-forming nucleating agent, the content of the pore-forming nucleating agent may include 2% by mass or more based on the total amount of the resin film from the viewpoint of forming sufficient pores in the resin film. Preferably, 4% by mass or more is included, more preferably 10% by mass or more, still more preferably 14% by mass or more. On the other hand, from the viewpoint of suppressing communication between pores in the film, the content is preferably 50% by mass or less, more preferably 40% by mass or less, and more preferably 30% by mass or less, based on the total amount of the resin film. More preferably, it is particularly preferably 25% by mass or less.

As the pore-forming nucleating agent, an inorganic fine powder alone, an organic filler alone, or a combination of an inorganic fine powder and an organic filler can be used with the above content. Each content ratio in the case of using combining inorganic fine powder and an organic filler is not specifically limited. For example, those containing 10 to 99% by mass of the inorganic fine powder, 20 to 90% by mass, or 30 to 80% by mass of the inorganic fine powder can be used with respect to the total amount of the pore-forming nucleating agent. Can be used.

The content rate of the vacancy-forming nucleating agent is as described above, but if the content rate of the vacancy-forming nucleating agent is equal to or higher than the lower limit of the above preferred range, a sufficient number of charges are accumulated in the stretching step described later. Therefore, it is easy to obtain holes having a size suitable for the purpose, and it is easy to obtain desired piezoelectric performance. On the other hand, if the content of the pore-forming nucleating agent is less than or equal to the upper limit of the above preferred range, a decrease in film strength due to excessive pore formation is likely to be suppressed, and repeated compressive force is applied to the obtained electret material. However, it can be expected that sufficient compression recovery properties are easily exhibited and that the piezoelectric performance is stabilized.

[Inorganic fine powder]
Among the pore-forming nucleating agents, inorganic fine powders are low in cost, and many products with different particle sizes are commercially available. Specific examples of usable inorganic fine powder include calcium carbonate, calcined clay, silica, diatomaceous earth, white clay, talc, titanium oxide, barium sulfate, alumina, zeolite, mica, sericite, bentonite, sepiolite, vermiculite, dolomite. , Wollastonite, glass fiber and the like, but are not particularly limited thereto. An inorganic fine powder can be used individually by 1 type or in combination of 2 or more types.

The volume average particle diameter of the inorganic fine powder (median diameter (D ₅₀ ) measured with a particle size distribution meter by laser diffraction) should be selected appropriately in consideration of forming pores of a size suitable for accumulating charges. There is no particular limitation. From the viewpoint that the formed pores have an appropriate size and desired piezoelectric performance can be easily obtained, the volume average particle size of the inorganic fine powder is preferably 3 μm or more, more preferably 4 μm or more, and more preferably 5 μm or more. More preferably it is. On the other hand, the formation of coarse pores prevents adjacent pores from communicating with each other to short-circuit the charge, making it difficult for the charge to accumulate, and suppressing the decrease in film strength due to the pores being too large. In the electret, the volume average particle size of the inorganic fine powder may be 30 μm or less from the standpoint that sufficient compression recovery can be achieved even when repeated compressive force is applied and the piezoelectric performance can be expected to be stable. Preferably, it is 20 μm or less, and more preferably 15 μm or less.

[Organic filler]
Among the pore-forming nucleating agents, the organic filler is available as spherical particles having a uniform particle diameter, and the pores formed in the porous resin film can be easily obtained in a uniform size and shape. . In addition, since the organic filler can function as a support in the pores even after the formation of the pores, the pores are not easily crushed, and the obtained electret exhibits sufficient compression recovery properties even when repeated compression force is applied. In addition, it can be expected that the piezoelectric performance is stabilized (pillar effect).

As the organic filler, it is preferable to select resin particles of a different type from the thermoplastic resin that is the main component of the porous resin film. For example, when the thermoplastic resin is a polyolefin resin, preferred organic fillers include those that are incompatible with polyolefin and do not have fluidity during kneading and stretching of the polyolefin resin. More specific examples include, but are not limited to, a crosslinked acrylic resin, a crosslinked methacrylic resin, a crosslinked styrene resin, and a crosslinked urethane resin. Resin particles made of these cross-linked resins are particularly preferably used because they can be obtained as spherical particles having a predetermined particle diameter and can easily adjust the size of the pores.

The organic filler is incompatible with the thermoplastic resin that is the main component of the porous resin film, but is melt-kneaded with the thermoplastic resin to form a sea-island structure. A desired hole may be formed by forming a hole core at the time of stretch molding. For example, when the thermoplastic resin is a polyolefin resin, specific examples of the organic filler include polyethylene terephthalate, polybutylene terephthalate, polycarbonate, nylon-6, nylon-6,6, cyclic olefin polymer, polystyrene, polymethacrylate, etc. Which has a melting point higher than that of the polyolefin resin (for example, 170 to 300 ° C.) or glass transition temperature (for example, 170 to 280 ° C.), and is melt-kneaded in the polyolefin resin that is a matrix resin. The thing which can be finely dispersed is mentioned. An organic filler can be used individually by 1 type or in combination of 2 or more types. Moreover, said inorganic fine powder and said organic filler can also be used together as a void | hole formation nucleating agent.

The volume average particle size of the organic filler (median diameter (D ₅₀ ) measured with a particle size distribution meter by laser diffraction) can be selected as appropriate in consideration of forming pores of a size suitable for accumulating charges. Yes, it is not particularly limited. From the viewpoint of easily forming the desired pore size and obtaining desired piezoelectric performance, the volume average particle diameter of the organic filler is preferably 3 μm or more, more preferably 4 μm or more, and more preferably 5 μm or more. More preferably. On the other hand, the formation of coarse pores prevents adjacent pores from communicating with each other to short-circuit the charge, making it difficult for the charge to accumulate, and suppressing the decrease in film strength due to the pores being too large. In the electret, it is preferable that the volume average particle size of the organic filler is 30 μm or less from the viewpoint that sufficient compressive recovery property can be expressed even when repeated compressive force is applied and the piezoelectric performance can be expected to be stable. More preferably, it is 20 μm or less, and further preferably 15 μm or less.

When the inorganic fine powder and the organic filler are used in combination as the pore-forming nucleating agent, one or more of the inorganic fine powders listed above are used in combination with one or more of the organic fillers listed above. be able to. Also in this case, for the same purpose as described above, the volume average particle size of the mixture is preferably in the range of 3 to 30 μm, more preferably in the range of 4 to 20 μm, and in the range of 5 to 15 μm. More preferably.

When the inorganic fine powder and the organic filler are used in combination, the volume average particle size may be used by combining the inorganic fine powder and the organic filler having a particle size within the same range individually. A mixture having a volume average particle diameter measured by a particle size distribution meter by laser diffraction in the same range may be used.

[Other materials]
If necessary, additives such as a dispersant, a heat stabilizer (antioxidant), and a light stabilizer can be arbitrarily added to the resin film.

In the case of adding a dispersant, from the viewpoint of suppressing the generation of unintended coarse pores or continuous pores due to poor dispersion of the pore-forming nucleating agent, 0.01% by mass or more is included based on the total mass of the resin film. The content is preferably 0.03% by mass or more, more preferably 0.05% by mass or more. On the other hand, from the viewpoint of moldability and charge retention of the resin film, it is preferably contained in an amount of 10% by mass or less, more preferably 5% by mass or less, and more preferably 2% by mass or less based on the total mass of the resin film. preferable. Specific examples of the dispersant include dispersants such as fatty acid, glycerin fatty acid, polyglycerin fatty acid ester, sorbitan fatty acid ester, silane coupling agent, poly (meth) acrylic acid or salts thereof, and the like. There is no particular limitation.

When the heat stabilizer is added, it is usually added in the range of 0.001 to 1% by mass based on the total mass of the resin film. Specific examples of the heat stabilizer include sterically hindered phenol-based, phosphorus-based, and amine-based heat stabilizers, but are not particularly limited thereto. Although these heat stabilizers do not reach metal soaps, they are considered to have charge retention performance. In particular, metal soaps are used in combination with sterically hindered phenols and phosphorus heat stabilizers to maintain charge. There is a tendency to improve performance.
Originally, the heat stabilizer preferably has a high melting point from the viewpoint of charge retention performance, but in order to uniformly disperse the heat stabilizer in the energy conversion film, the heat stabilizer preferably has a low melting point. Accordingly, the melting point of the heat stabilizer is preferably in the same melting point range as that of the metal soap.
In order to sufficiently exhibit the charge retention performance of the metal soap, the compounding ratio of the metal soap to the total amount of the heat stabilizer is preferably 1: 0.2 to 1: 100, more preferably 1: 0.5 to 1:50. Preferably, 1: 1 to 1:10 is more preferable, and 1: 2 to 1: 5 is most preferable.

When adding a light stabilizer, it is usually added within a range of 0.001 to 1% by mass based on the total mass of the resin film. Specific examples of the light stabilizer include sterically hindered amine-based, benzotriazole-based, and benzophenone-based light stabilizers, but are not particularly limited thereto.

[Layer structure of resin film or porous resin film]
The resin film or porous resin film may be a single-layer film made of the resin composition having the above composition, or may be a multi-layered resin film having at least one layer of the film. The resin film or porous resin film is preferably a resin film having a multilayered structure (laminated resin film) having at least a core layer and a skin layer, and has a three-layer structure of skin layer / core layer / skin layer. More preferred.

[Core layer]
When the resin film has a laminated structure having a core layer and a skin layer, the above resin film or porous resin film may be used as a core layer, and a skin layer may be further provided on the core layer. Hereinafter, the resin film or the porous resin film may be referred to as a core layer.

The thickness of the core layer measured by the method described later is preferably 10 μm or more, more preferably 20 μm or more, further preferably 30 μm or more, and particularly preferably 40 μm or more. This makes it easy to secure the volume necessary for accumulating internal charges that function effectively for energy conversion, and in the case of a porous resin film, the number of pores of an appropriate size for accumulating internal charges is uniform in the desired quantity. Easy to form. On the other hand, the thickness of the core layer is preferably 500 μm or less, more preferably 300 μm or less, further preferably 150 μm or less, and particularly preferably 120 μm or less. As a result, when electretization (charge injection treatment, direct current high-voltage discharge treatment) described later is performed to electret the resin film to form an energy conversion film, it is possible to cause charges to reach the inside of the layer. It is easy to demonstrate the expected performance.

[Skin layer]
The skin layer is laminated on at least one surface of a resin film or a porous resin film (core layer). The skin layer is preferably laminated on at least one side of the core layer as a layer protecting the core layer, and more preferably laminated on both sides of the core layer. By providing a skin layer on the surface of the core layer, it is possible to barrier metal soap that may bleed out from the resin film, and the pores formed in the porous resin film communicate with the outside. The stored charge can be easily prevented from being discharged into the atmosphere, the surface strength of the porous resin film can be improved, and the adhesion to the electrode can be improved by smoothing the surface.

The skin layer is also preferably made of a film containing a thermoplastic resin. As a thermoplastic resin which comprises a skin layer, what was enumerated by the term of the thermoplastic resin used for a resin film can be used.

Here, the skin layer may or may not contain a metal soap like the core layer. In order to make the skin layer a protective layer for the core layer, the skin layer preferably contains no metal soap. When a skin layer contains a metal soap, it is preferable to make the compounding quantity smaller than that in a core layer.

The skin layer preferably has a composition that is less likely to form vacancies than the core layer, or a structure having a lower porosity than the core layer. The formation of such a skin layer can be achieved by using a technique in which the content of the pore-forming nucleating agent is less than that of the core layer, or by using the volume average particle size of the pore-forming nucleating agent used in the skin layer in the core layer. This can be achieved by a technique of making the volume average particle size of the nucleating agent smaller than the volume average particle diameter, a technique of forming a core layer by biaxial stretching and a skin layer by uniaxial stretching, or the like, and making a difference between the stretching ratios.

The skin layer may or may not contain a pore-forming nucleating agent. From the viewpoint of improving the physical strength of the skin layer and improving the durability of the core layer, it is preferable not to contain a pore-forming nucleating agent. Further, from the viewpoint of improving the dielectric constant of the skin layer and modifying the electrical characteristics of the core layer, it is preferable to contain a pore-forming nucleating agent. When the skin layer contains a pore-forming nucleating agent, those listed in the section of the pore-forming nucleating agent used for the porous resin film can be used. Here, as the pore-forming nucleating agent for the skin layer, the same or different types of pore-forming nucleating agent for the porous resin film may be used.

Particularly, organic fillers are generally suitable for modifying the electrical properties of the skin layer because they have a dielectric constant generally higher than that of thermoplastic resins used for porous resin films. In particular, when a resin having a relatively low dielectric constant, such as a polyolefin resin, is used as the thermoplastic resin for the skin layer, by adding an organic filler to the skin layer, the dielectric can be applied when a high voltage is applied during electretization. Due to the effect, the charge can easily reach the inside of the resin film (inside the core layer). On the other hand, after the electretization treatment, an effect of retaining the electric charge inside the resin film without escaping can be obtained due to the low dielectric properties of the polyolefin resin as the main component.

When the pore forming nucleating agent is contained in the skin layer, it is preferable to use the same dispersing agents as those listed in the section of the dispersing agent used for the porous resin film.

The skin layer is preferably stretched. The stretching process described in detail below can improve the uniformity of the thickness (film thickness) of the skin layer and the uniformity of electrical characteristics such as the withstand voltage. If the thickness of the skin layer is not uniform, local discharge concentration is likely to occur in the thin portion of the skin layer during charge injection using a high voltage, so high voltage application for effective charge injection is performed. It tends to be difficult.

Note that the skin layer may have not only a single layer structure but also a multi-layer structure having two or more layers. In the case of a multilayer laminated structure, a porous resin having a multilayer laminated structure having higher charge retention performance by changing the type and content of the thermoplastic resin, pore-forming nucleating agent and dispersant used in each layer The film design becomes easy.

When providing the skin layer on both the front and back surfaces of the core layer, the composition, configuration, thickness, etc. of the front and back skin layers may be the same or different.

When the skin layer is provided on the surface of the core layer, the thickness of the skin layer is not particularly limited, but is preferably 0.1 μm or more, more preferably 0.3 μm or more, and 0.5 μm or more. Is more preferable, and 0.7 μm or more is particularly preferable. As a result, it becomes easy to provide the skin layer uniformly, and uniform charge injection and improvement in dielectric strength can be expected. On the other hand, the thickness of the skin layer is preferably 100 μm or less, more preferably 50 μm or less, further preferably 30 μm or less, and particularly preferably 10 μm or less. Thereby, when injecting electric charge into the porous resin film having a multilayer laminated structure, the electric charge tends to easily reach the core layer inside the film.

The skin layer is preferably thinner than the core layer. Since the skin layer is a layer that is less likely to undergo elastic deformation in the thickness direction than the core layer, by suppressing the thickness of the skin layer, the compression elastic modulus of the porous resin film or the like does not decrease, and the energy conversion efficiency is improved. Easy to maintain.

Therefore, the ratio of the thickness of the core layer to the thickness of the skin layer (core layer / skin layer) is preferably 1.1 to 1000, more preferably 2 to 300, and more preferably 5 to 150. More preferred is 10-50. The equivalent value is converted from the total value when there are multiple skin layers.

[Formation of resin film]
Various conventionally known methods can be used for the production of the resin film. For example, when the resin film is a single-layer film, the resin composition containing the above raw materials may be melt-kneaded, extruded from a single die, and stretched as necessary. In addition, when the resin film has a multilayer laminated structure having a core layer and a skin layer, both of them can be obtained by a co-extrusion method using a multilayer die using a feed block or a multi-manifold or an extrusion lamination method using a plurality of dies. A laminated multilayer resin film can be produced. Furthermore, a resin film can also be produced by a method combining a coextrusion method using a multilayer die and an extrusion lamination method.

The uniformity of the thickness of the resin film is important because the electric charge injection efficiency is improved because the withstand voltage is improved, and the piezoelectric efficiency of the resulting energy conversion film is improved.

The resin film is preferably a stretched film stretched in at least one direction. By stretching, the uniformity of the thickness of the resin film is improved. In the case of a porous resin film, a large number of pores are formed inside by stretching. In the case of a resin film having a multilayer laminated structure having a core layer and a skin layer, it is preferable that the skin layer is laminated on the core layer and then stretched in at least one axial direction. By stretching after laminating the skin layer on the core layer, the uniformity of the film thickness is improved as compared with laminating stretched films, and as a result, the electrical characteristics are improved.

It is desirable that the pores formed in the porous resin film by stretching have a relatively large individual volume, a relatively large number, and shapes independent from each other, from the viewpoint of maintaining electric charge. The size of the holes is easier to extend in the biaxial direction than in one direction. In particular, the film stretched in the biaxial direction of the width direction and the flow direction can form a disk-like hole extending in the plane direction around the hole-forming nucleating agent. Therefore, positively and negatively polarized charges are easily stored, and the charge holding performance is excellent. Therefore, the porous resin film is preferably a biaxially stretched film.

The stretching of the resin film can be performed by various known methods. Specifically, a longitudinal stretching method using the peripheral speed difference of the roll group, a lateral stretching method using a tenter oven, a sequential biaxial stretching method in which the longitudinal stretching and the lateral stretching are performed in the normal order or reverse order, a rolling method, Examples thereof include a simultaneous biaxial stretching method using a combination of a tenter oven and a linear motor, and a simultaneous biaxial stretching method using a combination of a tenter oven and a pantograph. Moreover, the simultaneous biaxial stretching method by the tubular method which is a stretching method of an inflation film can be mentioned.

The temperature at the time of stretching is preferably 1 to 70 ° C. lower than the melting point of the crystal part of the main thermoplastic resin from the glass transition temperature of the main thermoplastic resin (used most by mass ratio) used for the resin film. Specifically, when the thermoplastic resin is a propylene homopolymer (melting point 155 to 167 ° C.), it is preferably within the range of 100 to 166 ° C., and when it is a high density polyethylene (melting point 121 to 136 ° C.). Is preferably in the range of 70 to 135 ° C. In addition, when stretching a resin film having a multilayer laminated structure, considering the stretching efficiency of the layer with the largest set basis weight (usually the core layer) or the layer with the highest set porosity (usually the core layer), It is preferable to set the stretching temperature. Of course, if the stretching temperature is determined by using thermoplastic resins having different melting points or glass transition points for the core layer and the skin layer of the resin film, the porosity of each layer can be adjusted.

The stretching ratio is not particularly limited, and may be appropriately determined in consideration of the stretching characteristics of the thermoplastic resin used for the resin film, the set porosity described above, and the like. For example, when a propylene homopolymer or a copolymer thereof is used as the thermoplastic resin, the stretching ratio is preferably 1.2 times or more, more preferably 2 times or more when stretching in a uniaxial direction. On the other hand, the upper limit side is preferably 12 times or less, and more preferably 10 times or less. Moreover, when extending | stretching to a biaxial direction, 1.5 times or more are preferable by area stretch ratio (product of a vertical magnification and a horizontal magnification), and 4 times or more are more preferable. On the other hand, the upper limit side is preferably 60 times or less, and more preferably 50 times or less.

When using other thermoplastic resins, the draw ratio is preferably 1.2 times or more and more preferably 2 times or more when uniaxially drawn. On the other hand, 10 times or less is preferable and 5 times or less is more preferable. Moreover, when extending | stretching to a biaxial direction, 1.5 times or more are preferable by area stretch ratio, and 4 times or more are more preferable. On the other hand, the upper limit side is preferably 20 times or less, and more preferably 12 times or less.

When the porous resin film is stretched in the biaxial direction, it is possible to set the vertical and horizontal magnifications to the same magnification as much as possible to form disk-like pores that are easy to accumulate charges, and to cross sections in any direction. It is easy to adjust the shape and frequency of the holes observed in the above to the preferable range of the present invention. Therefore, when stretching in the biaxial direction, the ratio of the vertical magnification and the horizontal magnification is preferably 0.4 or more, more preferably 0.5 or more, and further preferably 0.7 or more. Preferably, it is 0.8 or more. On the other hand, the upper limit side is preferably 2.5 or less, more preferably 2.0 or less, further preferably 1.5 or less, and particularly preferably 1.3 or less. The stretching speed is preferably in the range of 20 to 350 m / min from the viewpoint of stable stretch molding.

[surface treatment]
The resin film can be subjected to a surface treatment by a known method on one side or both sides in order to enhance adhesion with other materials such as electrodes described later. Specific examples of the surface treatment include techniques such as corona discharge treatment, flame plasma treatment, and atmospheric pressure plasma treatment. Moreover, the adhesiveness of a resin film can be improved more by substituting the processing environment of these surface treatments, and the generation source of a plasma with desired gas. Furthermore, the adhesion can be improved by washing the resin film surface with an acid such as hydrochloric acid, nitric acid, sulfuric acid or the like.

[Anchor coat layer]
The resin film may be provided with an anchor coat layer on one side or both sides in order to improve adhesion to the electrode described later.

In the anchor coat layer, it is preferable to use a polymer binder from the viewpoint of improving the adhesion between the resin film and the electrode. Specific examples of the polymer binder include polyethyleneimine, polyethylenimine-based polymers such as C1-C12 alkyl-modified polyethyleneimine, poly (ethyleneimine-urea); polyamine polyamide ethyleneimine adduct, and polyamine Polyamine polyamide polymers such as polyamide epichlorohydrin adducts; acrylic amide-acrylic ester copolymers, acrylic amide-acrylic ester-methacrylic ester copolymers, polyacrylamide derivatives, oxazoline group-containing acrylic esters Acrylic ester polymers such as polymer based polymers; polyvinyl alcohol polymers including polyvinyl alcohol and modified products thereof; water soluble resins such as polyvinyl pyrrolidone and polyethylene glycol; and chlorinated polypropylene Modified polypropylene polymers such as ethylene, maleic acid modified polypropylene, acrylic acid modified polypropylene; and the like; polyvinyl acetate, polyurethane, ethylene-vinyl acetate copolymer, polyvinylidene chloride, acrylonitrile-butadiene copolymer, and Non-water-soluble resin such as polyester; Among these, a polyethyleneimine polymer, a polyamine polyamide polymer, a polyvinyl alcohol polymer, and a modified polypropylene polymer are preferable because of excellent adhesion to a resin film.

As a method of providing an anchor coat layer on a resin film, various conventionally known methods can be used, and are not particularly limited. However, a method of coating a coating liquid containing the above polymer binder on a resin film is preferable. Specifically, it can be formed by forming a coating film of the coating solution on a resin film using a known coating apparatus and drying the coating film.

When the polymer binder is a water-soluble resin, the coating liquid is an aqueous solution or water dispersion. When the polymer binder is a water-insoluble resin, the polymer binder is known as an organic solvent solution or water dispersion. It is prepared so that it can be applied by a method.

Specific examples of coating equipment include die coaters, bar coaters, comma coaters, lip coaters, roll coaters, curtain coaters, gravure coaters, squeeze coaters, spray coaters, blade coaters, reverse coaters, air knife coaters, and size presses. Although a coater etc. are mentioned, it is not specifically limited to these.

When the anchor coat layer is provided on the resin film, the basis weight is not particularly limited, but is preferably 0.001 g / m ² or more in terms of solid content from the viewpoint of improving the adhesion between the resin film and the electrode. .005g / ^{m 2} or more preferably, 0.01 g / ^{m 2} or more is particularly preferable. On the other hand, from the viewpoint of maintaining the film thickness of the anchor coat layer is a coating layer uniformly, its basis weight is preferably 5 g / m ² or less in terms of solid content, more preferably not more than ^{3g / m 2, 1g / m} 2 The following are particularly preferred: In addition, when the film thickness of the anchor coat layer that is the coating layer cannot be kept uniform, the uniformity in the surface direction of the electrical characteristics of the resin film is impaired due to the fluctuation of the film thickness, or the anchor coat layer itself has insufficient cohesive strength. Because the adhesion between the resin film and the electrode is reduced, or the surface resistance value of the anchor coat layer is reduced to less than 1 × 10 ¹³ Ω, and the charge easily escapes through the surface when the resin film is electretized. In addition, it may be difficult for charges to be injected into the resin film, and the charge may not reach the inside of the resin film, and the desired performance of the present invention may be difficult to be exhibited.

The timing at which the anchor coat layer is provided on the resin film may be before or after the electret treatment described in detail later.

[Pressure treatment]
The porous resin film can further expand the internal pores by pressure treatment. Pressurization treatment places a porous resin film in a pressure vessel, pressurizes the inside of the vessel with a non-reactive gas, so that the non-reactive gas penetrates into the pores, and then releases the porous resin film under no pressure. To do.

Specific examples of the non-reactive gas to be used include nitrogen, carbon dioxide, an inert gas such as argon and helium, or a mixed gas or air thereof. Even when a gas other than the non-reactive gas is used, the expansion effect can be obtained, but it is desirable to use the non-reactive gas from the viewpoint of safety during the pressurizing process and safety of the obtained porous resin film. The treatment pressure during the pressure treatment is not particularly limited, but is preferably in the range of 0.2 to 10 MPa, more preferably 0.3 to 8 MPa, and still more preferably 0.4 to 6 MPa. If the pressure is less than 0.2 MPa, the pressure is low, so that a sufficient expansion effect tends not to be obtained. On the other hand, when the pressure exceeds 10 MPa, the pore walls cannot withstand the internal pressure when released under non-pressurization, and the pores tend to be broken, making it difficult to maintain the pores as independent holes. The treatment time of the pressure treatment is not particularly limited, but is preferably 1 hour or more, more preferably 1 to 50 hours. In the case of a porous resin film in which the treatment time is less than 1 hour, it is difficult to sufficiently fill the nonreactive gas in the pores, or the pores are sufficiently filled with the nonreactive gas in less than 1 hour. During the heat treatment, the non-reactive gas is dissipated and it is difficult to obtain a stable expansion effect.

In addition, when pressurizing the winding roll of the porous resin film, a roll wound together with the buffer sheet is prepared in advance so that the non-reactive gas can easily penetrate into the winding roll. It is desirable to process. As a specific example of the buffer sheet, a foamed polystyrene sheet, a foamed polyethylene sheet, a foamed polypropylene sheet, a nonwoven fabric, a woven fabric, a paper or the like having a continuous void can be used.

[Heat treatment]
In the porous resin film subjected to the pressure treatment, it is preferable to perform a heat treatment in order to maintain the expansion effect. A porous resin film expand | swells by performing a pressurization process and releasing under non-pressurization. However, if left as it is, the non-reactive gas that has penetrated into the pores gradually escapes, and the porous resin film may return to its original thickness. Therefore, it is desirable to maintain the expansion effect even after the inside of the pores has been reduced to atmospheric pressure by performing heat treatment on the expanded porous resin film to promote crystallization of the thermoplastic resin. This heat treatment can be performed within a temperature range from the glass transition temperature of the thermoplastic resin mainly used for the porous resin film to the melting point of the crystal part. Specifically, for example, when the thermoplastic resin is a propylene homopolymer (melting point: 155 to 167 ° C.), the temperature is in the range of 80 to 160 ° C. Moreover, a well-known method can be used for the heating method. Specific examples include hot air heating with hot air from a nozzle, radiation heating with an infrared heater, contact heating with a roll having a temperature control function, and the like, but are not particularly limited thereto. In addition, since the elastic modulus of the porous resin film is reduced during the heat treatment, and the load is applied, the pores are apt to be crushed. There is a tendency.

[Energy conversion film]
By carrying out the process (electretization process) of injecting charges into the resin film or the porous resin film, and making it into an electret, a charged resin film holding an electric charge inside the film, that is, an energy conversion film is obtained.

[Electretization]
As an electret process, several processing methods are mentioned. For example, a method of holding both surfaces of a resin film with a conductor and applying a DC high voltage or a pulsed high voltage (electroelectretization method), or a method of electretization by irradiating a resin film with γ rays or electron beams (radio) An electret method) is known.

Among these, the electretization method (electroelectretization method) using DC high-voltage discharge has a small apparatus and a small burden on workers and the environment, and is a high-molecular material such as a porous resin film. It is suitable for electretization treatment and is preferred.

As an example of an electret apparatus that can be used here, an electret apparatus using DC high-voltage discharge is shown in FIG. As shown in FIG. 3, this electretization apparatus is a device in which a resin film 13 is fixed and a predetermined voltage is applied between a needle electrode 11 and a ground electrode 12 connected to a DC high voltage power source 10. By the electretization process by this direct current high voltage discharge, the resin film 13 can accumulate | store many electric charges inside a film.

The applied voltage during electret treatment is the thickness of the resin film, the porosity, the material of the thermoplastic resin and pore forming nucleating agent used in the resin film, the processing speed, the shape, material and size of the electrode used, and finally The energy conversion film to be obtained can be changed depending on the desired charge amount and the like, and may be appropriately set in consideration of these, and is not particularly limited, but is preferably 5 kV or more, more preferably 6 kV or more, and further 7 kV or more. preferable. As a result, a sufficient amount of charge can be injected and desirable piezoelectric performance tends to be exhibited. On the other hand, the applied voltage for electretization is preferably 100 kV or less, more preferably 70 kV or less, and even more preferably 50 kV or less. As a result, a local spark discharge occurs during the electretization process, causing a partial destruction such as pinholes in the resin film, and a current is transmitted from the surface of the resin film to the end face through the end surface during the electretization process. It tends to be easy to avoid a phenomenon of flowing and deteriorating the efficiency of electretization.

The treatment temperature at the electretization treatment may be set as appropriate, and is not particularly limited. However, it is desirable that the treatment temperature be higher than the glass transition temperature of the main thermoplastic resin used for the resin film and lower than the melting point of the crystal part. If the treatment temperature is equal to or higher than the glass transition point, the molecular motion of the amorphous portion of the thermoplastic resin is active, and a molecular arrangement suitable for a given charge is formed, so that an efficient electretization process is possible. Further, when the treatment temperature is equal to or higher than the melting point of the metal soap, the metal soap molecules also have an arrangement suitable for the given charge, and therefore, more efficient electretization can be performed. On the other hand, if the processing temperature exceeds the melting point of the main thermoplastic resin used for the resin film, the resin film itself cannot maintain its structure, making it difficult to obtain the desired performance of the present invention. There is a tendency.

In the electretization process, an excessive charge may be injected into the resin film intentionally or unintentionally. In this case, since the energy conversion film may discharge after processing and cause inconvenience in the post-processing process, the charge removal of the charged resin film may be performed after the electret processing.

As this charge removal treatment, a known method using a voltage application type charge remover (ionizer), a self-discharge type charge remover, or the like can be used. The neutralization treatment using these general static eliminators can remove the surface charge of the charged resin film, but cannot completely remove the charge accumulated inside the charge resin film, particularly in the pores of the core layer. . Accordingly, the performance of the electret material is not greatly reduced by the charge removal process. Therefore, the discharge phenomenon of the electret can be prevented by performing such a charge removal process to remove excess charges on the surface of the charged resin film.

[Energy conversion element]
By providing an electrode to be described later on at least one surface of the above-described energy conversion film, an energy conversion element that inputs and outputs power and electric signals can be obtained. The energy conversion element preferably includes electrodes on both front and back surfaces of the energy conversion film in order to more efficiently input and output electrical signals.

The installation timing of the electrode is not particularly limited, and may be performed, for example, on the resin film before the electret treatment or on the charged resin film (energy conversion film) after the electret treatment. If an electrode is installed in the energy conversion film after the electretization treatment, it is possible to prevent part of the injected charge from being released through the electrode during the electretization treatment. However, when a load such as heat is applied to the charged resin film during the subsequent electrode installation, a part of the injected charge is dissipated, and the piezoelectric performance may be slightly deteriorated. At present, it is preferable that an electrode is previously provided on the resin film before the electretization process, and then the above electretization process is performed based on the performance of the finally obtained energy conversion element.

[electrode]
By providing an electrode on at least one surface of an energy conversion film obtained by electretizing a resin film, an energy conversion element capable of inputting and outputting electric power can be obtained. Usually, a pair of electrodes is provided on both surfaces (front surface and back surface) of the energy conversion film. Examples of the electrode include a thin film formed of a known conductive material such as metal particles, conductive metal oxide particles, carbon-based particles, or conductive resin. Moreover, as an electrode, the coating film by printing or coating of a conductive paint, a metal vapor deposition film, etc. are mentioned.

Examples of conductive materials include metal particles such as gold, silver, platinum, copper, silicon; tin-doped indium oxide (ITO), antimony-doped tin oxide (ATO), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide, etc. Conductive metal oxide particles: carbon particles such as graphite, carbon black, ketjen black, carbon nanofiller, carbon nanotubes, acrylic resins, urethane resins, ether resins, ester resins, epoxy resins , Vinyl acetate resin, vinyl chloride resin, vinyl chloride-vinyl acetate copolymer, amide resin, melamine resin, phenol resin, vinyl alcohol resin, modified polyolefin resin, etc. It is done. Moreover, the solution or dispersion liquid of conductive resins, such as a polyaniline type, a polypyrrole type, and a polythiophene type, are mentioned.

Specific examples of printing methods in the case where a conductive paint is used as ink and provided by printing include screen printing, flexographic printing, gravure printing, inkjet printing, letterpress printing, offset printing, and the like. In addition, specific examples of coating apparatuses that use conductive paint as a paint and are provided by coating include die coaters, bar coaters, comma coaters, lip coaters, roll coaters, curtain coaters, gravure coaters, and spray coaters. , Blade coater, reverse coater, air knife coater and the like.

As a specific example of a metal vapor deposition film, metal such as aluminum, zinc, gold, silver, platinum, nickel is vaporized under reduced pressure and vapor deposited on the surface of the resin film, and a metal thin film is directly formed on the surface of the resin film. Or a metal thin film formed by vapor-depositing a metal such as aluminum, zinc, gold, silver, platinum, nickel on a carrier such as a polyethylene terephthalate (PET) film, etc. Can be mentioned.

The electrode is a resin film or energy formed by previously forming a conductive paint film or metal vapor deposition film on a dielectric film such as a polyethylene terephthalate film or a polypropylene film so that the conductive surface is on the outside. It may be provided by pasting with a conversion film. Specific examples of the bonding method include known methods such as dry lamination, wet lamination, and extrusion lamination.

Electrode from the spirit easily make power input and output, JIS K7194: 1994 a surface resistivity measured by the four-terminal method in accordance with the "resistivity test method by a four probe method of conductive plastic" is 1 × 10 ^- It is preferably ³ Ω / □ to 9 × 10 ⁷ Ω / □, and more preferably 1 × 10 ⁻¹ Ω / □ to 9 × 10 ⁴ Ω / □. When the resistance value of the electrode exceeds 9 × 10 ⁷ Ω / □, the electric signal transmission efficiency is poor, and the performance as a material for an electric / electronic input / output device tends to be lowered. On the other hand, when an electrode of less than 1 × 10 ⁻³ Ω / □ is provided, and the electrode is provided by coating, it is necessary to provide a thick electrode. In some cases, the pores of the porous resin film are crushed or the resin film is thermally contracted. Also, when the electrodes are provided by metal vapor deposition, the resin film may be similarly deformed by the heat of the metal deposited.

The thickness of the electrode is not particularly limited, but is preferably 0.1 μm or more, more preferably 1 μm or more, and further preferably 5 μm or more. The thickness of the electrode is preferably 200 μm or less, more preferably 50 μm or less, and further preferably 20 μm or less.

[Thickness of resin film]
In this specification, the thickness of the resin film is a value obtained by measuring the total film thickness using a thickness meter based on JIS K7130: 1999 “Plastics—Film and Sheet—Thickness Measurement Method”. Further, when the resin film is a resin film having a multilayer laminated structure, the thickness of each layer constituting the resin film is determined by cooling the sample to be measured with liquid nitrogen to a temperature of −60 ° C. or lower and placing the sample on a glass plate. A razor blade is applied at a right angle and cut to create a sample for cross-section measurement, and the resulting sample is observed using a scanning electron microscope to determine the boundary line of each layer from the hole shape and composition appearance. And the ratio which each layer thickness calculated | required from an observation image occupies for the total thickness of a resin film is set to the value calculated by multiplying the said film total thickness calculated | required using the thickness meter by the said ratio of each layer thickness.

[Surface resistivity of resin film]
In this specification, the surface resistivity of the resin film is determined under the conditions of a temperature of 23 ° C. and a relative humidity of 50% using a double ring electrode according to JIS K6911: 1995 “General Test Method for Thermosetting Plastics”. It is set as the value calculated based on the following formula 2 from the surface resistance measured in (1).

The resin film is preferably insulative, and the surface resistivity of at least one surface is preferably 1 × 10 ¹³ Ω / □ or more, and more preferably 5 × 10 ¹³ Ω / □ or more. As a result, when the electretization process is performed, the injected charge is difficult to escape through the surface, and efficient charge injection is easy to perform. On the other hand, the surface resistance of at least one surface of the resin film is preferably 9 × 10 ¹⁷ Ω / □ or less, and more preferably 5 × 10 ¹⁶ Ω / □ or less. This prevents dust and dirt from adhering to the resin film, and it is easy to suppress the phenomenon that local discharge occurs along the dust and dust during the electretization process and the efficient electretization process is hindered.

[Surface resistivity of electrode]
In this specification, the surface resistivity of the electrode is calculated based on the following equation 3 from the resistance value measured by the four-terminal method in accordance with JIS K7194: 1994 “Resistivity Test Method by Conductive Plastic Four-Probe Method”. Value.

[Plane view area of energy conversion film and energy conversion element]
Since the energy conversion film and the energy conversion element of the present invention use the charged resin film as described above, they are relatively low-cost unlike semiconductor materials that have been widely used as electro-mechanical energy conversion materials. For example, it is easy to increase the area of about 10 to 50,000 cm ^{2 in} a plan view of the film. In the case of constituting a large area energy conversion film and energy conversion element, the area in plan view may be appropriately set in consideration of the desired performance, physical restrictions on the installation location, etc., and is not particularly limited. 30,000 cm ² is preferable, and 50 to 25,000 cm ² is more preferable.

[Maximum voltage]
In the energy conversion element, the maximum voltage (average value) generated by impact after heat treatment is preferably 5 mV or more, more preferably 10 mV or more, and more preferably 20 mV or more in terms of practical performance of the energy conversion element. Is more preferable, and 30 mV or more is particularly preferable. Although an upper limit is not specifically limited, It is preferable that it is 300 mV or less, It is more preferable that it is 200 mV or less, It is further more preferable that it is 100 mV or more, It is especially preferable that it is 50 mV or less. In this specification, the heat treatment before the measurement of the maximum voltage is performed by holding the energy conversion element at 85 ° C. for 14 days. The maximum voltage is an iron ball having a diameter of 9.5 mm and a mass of 3.5 g from a height of 8 mm in a vertical direction on an energy conversion element placed on a horizontal plane at a temperature of 23 ° C. and a relative humidity of 50%. The maximum voltage generated by the impact when it is naturally dropped is measured 10 times, and the average value of the maximum voltage is calculated.

Hereinafter, the present invention will be described in more detail using production examples, examples, comparative examples, and test examples. The materials, amounts used, ratios, operations, and the like shown below can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. In addition,% described below represents mass% unless otherwise specified.

[Preparation Example of Resin Composition]
The thermoplastic resin (propylene homopolymer and high-density polyethylene) listed in Table 1, metal soap, heat stabilizer, and pore-forming nucleating agent (heavy calcium carbonate powder) are mixed in the proportions shown in Table 1 (units). : Mass%), melt kneaded with a twin-screw kneader set at 210 ° C., then extruded into a strand with an extruder set at 230 ° C., cooled and cut with a strand cutter, and resin composition Pellets of items ah, j, k, and mr were made.

[Production Examples 1 to 14, 16]
After melt kneading each of the resin composition for the front skin layer, the resin composition for the core layer, and the resin composition for the back skin layer described in Table 2 with three extruders set at 230 ° C., It is supplied to a feed block type multi-layer die set at 250 ° C., laminated in the die so as to be in the stacking order shown in Table 2, and extruded into a sheet shape. An unstretched sheet having a constitution was obtained.
The obtained unstretched sheet is heated to the longitudinal temperature described in Table 2 using a heating roll, and the longitudinal direction described in Table 2 is used in the longitudinal direction (MD direction) using the peripheral speed difference of the roll group. A uniaxially stretched sheet was obtained by stretching at a magnification of. Next, the obtained uniaxially stretched sheet was cooled to 60 ° C., reheated to the temperature in the transverse direction described in Table 2 using an oven, and transversely (TD direction) described in Table 2 using a tenter. After stretching at a direction magnification, it was further heated to 160 ° C. using an oven for annealing treatment to obtain a biaxially stretched sheet.
The obtained biaxially stretched sheet was cooled to 60 ° C., the ears were slit, the corona surface discharge treatment was performed on both sides, and the resin films of Production Examples 1 to 14 and 16 having the physical properties shown in Table 2 (whichever Also obtained a porous resin film having pores inside. The surface resistivity of the obtained resin film was all 10 ¹⁴ Ω / □ or more on both sides.

[Production Example 15]
A polyamine polyamide epichlorohydrin adduct solution (trade name: WS4024, manufactured by Seiko PMC Co., Ltd., solid content concentration: 25% by mass) as an anchor coating agent on both surfaces of the obtained resin film of Production Example 3 was water / 2-propanol = 9. Using a solution obtained by diluting 25 times with a mixed solution of 1/1, this was applied using a squeeze coater so that the coating amount after drying was 0.02 g / m ² , respectively. An anchor coat layer was provided by drying in an oven to obtain a resin film of Production Example 15. The surface resistivity of the obtained resin film was 10 ¹⁴ Ω / □ on both sides.

[Production Example 17]
According to the method for producing a synthetic resin foam sheet of Example 3 described in paragraphs 0051 to 0053 of JP-A-2014-074104, a resin film of Production Example 17 was obtained. The surface resistivity of the obtained resin film was 10 ¹⁴ Ω / □ on both sides.

[Examples 1 to 12, 17, 18, Comparative Examples 1 and 2]
Using a roll-to-roll vacuum deposition device on a PET film (trade name: E5200, manufactured by Toyobo Co., Ltd.) having a thickness of 12 μm, aluminum deposition is performed so that the thickness of the deposited film is 30 nm under a vacuum condition of 1 × 10 ⁻² Pa. The metal vapor deposition film whose surface resistivity of a vapor deposition surface is 1 ohm / square was created.
Next, a polyether adhesive (trade name: TM-317, manufactured by Toyo Morton) and an isocyanate curing agent (trade name: CAT-11B, manufactured by Toyo Morton) were mixed at a mass ratio of 50:50 to obtain ethyl acetate. Was diluted to produce an adhesive paint having a solid content concentration of 25%.
Next, the metal vapor-deposited film is cut into a square of 10 cm in length and 10 cm in width, and the entire surface is coated with a bar coater so that the coating thickness after drying the adhesive paint is 2 μm on the surface where the metal is not deposited. And dried in an oven at 40 ° C. for 1 minute to provide an adhesive layer on one side of the metal deposited film.
Next, the resin films obtained in Production Examples 1 to 14, 16, and 17 were cut into squares of 20 cm in length and 20 cm in width, and metal deposition was performed on the front and back center portions of the obtained cut films through an adhesive layer. After pasting the film so that the deposited film was the outermost layer, the adhesive was cured in an oven at 40 ° C. for 24 hours to obtain a resin film having electrodes on both sides.
The obtained resin film provided with electrodes on both sides is placed on the 12 ground electrodes of the electretization apparatus shown in FIG. 3 in which the distance between the needles of the needle electrodes is 10 mm and the distance between the needle electrodes and the ground electrode is 10 mm. Installed so that the surface faces the main electrode side, applying -10 KV DC voltage to the needle electrode for 5 seconds to carry out electret treatment, and Examples 1 to 12, 17, 18 and Comparative Examples shown in Table 3 The

energy conversion films

1 and 2 and the energy conversion elements of Examples 1 to 12, 17, 18 and Comparative Examples 1 and 2 were obtained.

[Example 13]
Using a roll-to-roll vacuum deposition device on a PET film (trade name: E5200, manufactured by Toyobo Co., Ltd.) having a thickness of 12 μm, aluminum deposition is performed so that the thickness of the deposited film is 30 nm under a vacuum condition of 1 × 10 ⁻² Pa. The metal vapor deposition film whose surface resistivity of a vapor deposition surface is 1 ohm / square was created.
Next, a polyether adhesive (trade name: TM-317, manufactured by Toyo Morton) and an isocyanate curing agent (trade name: CAT-11B, manufactured by Toyo Morton) were mixed at a mass ratio of 50:50 to obtain ethyl acetate. Was diluted to produce an adhesive paint having a solid content concentration of 25%.
Next, the metal vapor-deposited film is cut into a square of 10 cm in length and 10 cm in width, and the entire surface is coated with a bar coater so that the coating thickness after drying the adhesive paint is 2 μm on the surface where the metal is not deposited. And dried in an oven at 40 ° C. for 1 minute to provide an adhesive layer on one side of the metal deposited film.
Next, the resin film obtained in Production Example 15 was cut into a square of 20 cm in length and 20 cm in width, and a metal vapor-deposited film was formed as an outermost layer through an adhesive layer at the center of the back surface of the obtained cut film. Pasted to be.
Next, an aluminum foil having a thickness of 12 μm (trade name: My foil, manufactured by UACJ Foil Co., Ltd., surface resistivity: 3 × 10 ⁻³ Ω / □) is cut into a 10 cm long × 10 cm wide square, and the above-mentioned surface is provided on a low gloss surface The adhesive coating was applied to the entire surface using a bar coater so that the coating thickness after drying was 2 μm, dried in an oven at 40 ° C. for 1 minute, and then a cut film with a metal vapor deposited film attached as described above. After pasting on the center part of the surface, the adhesive was cured in an oven at 40 ° C. for 24 hours to obtain a resin film provided with electrodes on both sides.
The obtained resin film provided with electrodes on both sides is placed on the 12 ground electrodes of the electretization apparatus shown in FIG. 3 in which the distance between the needles of the needle electrodes is 10 mm and the distance between the needle electrodes and the ground electrode is 10 mm. Installed so that the surface faces the main electrode side, and applies an electret treatment by applying a -10 KV DC voltage to the needle electrode for 5 seconds. The energy conversion film of Example 13 and the energy conversion element of Example 13 Got.

[Example 14]
The resin film obtained in Production Example 15 was cut into a square of 20 cm in length and 20 cm in width, and silver ink (trade name: Doutite D-500, manufactured by Fujikura Kasei Co., Ltd., solid content was formed on the center of the back side of the obtained cut film. Concentration: 77% by mass) using a multipurpose printing tester (trade name: K303 Multicoater, manufactured by RK Print Coat Instruments) and a 400-line gravure plate, solid-printed on a 10 cm x 10 cm square, 80 ° C In an oven for 1 hour. Thereafter, the same silver ink is applied to the center portion of the surface of the cut film, using the same multipurpose printing tester and the same gravure plate, in a square of 10 cm in length and 10 cm in width so that the front and back printing positions are the same. Solid printing was performed and drying was performed in an oven at 80 ° C. for 24 hours to obtain a resin film having electrodes on both sides. The thickness of the obtained electrode was 2 μm on both sides, and the surface resistivity was 1Ω / □ on both sides.
The obtained resin film provided with electrodes on both sides is placed on the 12 ground electrodes of the electretization apparatus shown in FIG. 3 in which the distance between the needles of the needle electrodes is 10 mm and the distance between the needle electrodes and the ground electrode is 10 mm. The surface is set to face the main electrode side, and the electret treatment is performed by applying a -10 KV DC voltage to the needle electrode for 5 seconds. The energy conversion film of Example 14 and the energy conversion element of Example 14 Got.

[Example 15]
The resin film obtained in Production Example 15 was cut into a 20 cm long × 20 cm wide square, and a carbon ink (trade name: Dotite XC-3050, manufactured by Fujikura Kasei Co., Ltd. Using a screen printer (trade name: SSA-TF150E, manufactured by Ceria Corporation) and a 200-line screen plate, a solid is printed in a square of 10 cm in length and 10 cm in width, using an oven at 80 ° C. Dried for 1 hour. Thereafter, the carbon ink is applied to the center portion of the surface of the cut film using a screen printer and a screen plate so that the printing positions on the front and back sides are the same. It printed and dried in 80 degreeC oven for 24 hours, and the resin film provided with the electrode on both surfaces was obtained. The thickness of the obtained electrode was 10 μm on both sides, and the surface resistivity was 120Ω / □ on both sides.
The obtained resin film provided with electrodes on both sides is placed on the 12 ground electrodes of the electretization apparatus shown in FIG. 3 in which the distance between the needles of the needle electrodes is 10 mm and the distance between the needle electrodes and the ground electrode is 10 mm. The surface is set to face the main electrode side, and the electret treatment is performed by applying a -10 KV DC voltage to the needle electrode for 5 seconds. The energy conversion film of Example 15 and the energy conversion element of Example 15 Got.

[Example 16]
The resin film obtained in Production Example 15 was cut into a square of 20 cm in length and 20 cm in width, and a polythiophene-based ink (trade name: Olgacon ICP1050, manufactured by Agphagewald, solid content concentration) was formed at the center of the back surface of the obtained cut film. : 1.1% by mass) using a multipurpose printing tester (trade name: K303 Multicoater, manufactured by RK Print Coat Instruments Co., Ltd.) and a 100-line gravure plate, solid-printed on a 10 cm x 10 cm square, 80 It was dried in an oven at 0 ° C. for 1 hour. Thereafter, the polythiophene-based ink is applied to the center portion of the surface of the cut film, and the square of 10 cm in length and 10 cm in width is used so that the printing positions on the front and back are the same using the multipurpose printing tester and the gravure plate. Was solid-printed and dried in an oven at 80 ° C. for 24 hours to obtain a resin film having electrodes on both sides. The thickness of the obtained electrode was 0.2 μm on both sides, and the surface resistivity was 4 × 10 ⁴ Ω / □ on both the front and back sides.
The obtained resin film provided with electrodes on both sides is placed on the 12 ground electrodes of the electretization apparatus shown in FIG. 3 in which the distance between the needles of the needle electrodes is 10 mm and the distance between the needle electrodes and the ground electrode is 10 mm. Installed so that the surface faces the main electrode side, and applies an electret treatment by applying a -10 KV DC voltage to the needle-like electrode for 5 seconds. The energy conversion film of Example 16 and the energy conversion element of Example 16 Got.

<Test example>
From the obtained energy conversion elements of Examples 1 to 17 and Comparative Example 1, portions having electrodes were cut out to prepare samples each having a length of 10 cm and a width of 10 cm.
And the maximum voltage was measured with the following method using each obtained sample.
Next, each sample produced in the same manner was heat-treated in an oven set at 85 ° C. under severe conditions for 14 days, and the maximum voltage was measured by the following method using each sample after the heat treatment. Here, the heat treatment is performed for the purpose of promoting in a high temperature environment in order to evaluate the heat resistance of the obtained energy conversion element, unlike the heat treatment described above.

[Maximum voltage]
The maximum voltage was measured under a temperature 23 ° C. and relative humidity 50% environment using the falling ball test apparatus shown in FIG. Here, first,

lead wires

17 and 18 are formed using conductive tape (trade name: AL-25BT, manufactured by Sumitomo 3M) on the front and back electrodes of a sample 20 (energy conversion film 5) 10 cm long × 10 cm wide. The other ends of the

lead wires

17 and 18 are connected to a high-speed recorder 19 (trade name: GR-7000, manufactured by Keyence Corporation), and the insulating sheet 15 (soft chloride) of the falling ball test apparatus shown in FIG. A sample 20 is placed on a vinyl sheet (thickness 1 mm) so that the surface is on top, a glass plate 14 (thickness 8 mm) is placed on the upper surface of the sample 20, and a diameter of 9.5 mm and a mass is placed on the glass plate 14. A 3.5 g iron ball 16 was placed thereon.
Next, the iron ball 16 is naturally dropped from the glass plate 14 onto the sample 20 from a height of 8 mm in the vertical direction, the voltage signal from the sample 20 is taken into the high-speed recorder 19, and the maximum voltage generated by the impact of the falling ball is 10 times. The average value of the maximum voltage was calculated.

[Maintenance rate after heat treatment]
The ratio of the maximum voltage (average value) before and after the heat treatment calculated by the above method was obtained as a percentage and used as the maintenance rate after the heat treatment. Table 3 shows the calculated retention rate after heat treatment. The maintenance rate after heat treatment is preferably 1% or more, more preferably 2% or more, further preferably 3% or more, and particularly preferably 5% or more from the viewpoint of heat resistance.
From the data on the maintenance rate after heat treatment shown in Table 3, in the energy conversion film and the energy conversion element of the present invention, even when heat treatment was performed under severe conditions, the maintenance rate of the generated voltage reached about 140 to 800% of the comparative example. Furthermore, it was confirmed that the preferred embodiment has a particularly remarkable effect that cannot be achieved by the conventional product. From this, it can be inferred that the product of the present invention also has a considerably higher level of maintenance of the generated voltage at room temperature or at a higher temperature of about 40 to 60 ° C., which is a milder use condition.

The energy conversion film and energy conversion element of the present invention exhibit piezoelectricity at a temperature higher than the phase transition temperature of the energy conversion film material, and there is little deterioration in the piezoelectric performance even when exposed to a high temperature environment. Therefore, the energy conversion film and the energy conversion element of the present invention are electro-mechanical energy of speakers, headphones, microphones, ultrasonic sensors, pressure sensors, acceleration sensors, vibration control devices, etc. that may be used under high temperature conditions. It can be used widely and effectively as a module member for conversion. In particular, it can be used particularly effectively as a module member such as an acoustic sensor, a vibration sensor, and an impact sensor. Therefore, the present invention provides a measuring instrument, a control device, an abnormality diagnosis system, a security device, a stabilizer, It can be widely used as robots, percussion instruments, gaming machines, power generators, etc., and makes a great contribution to these industrial fields.

1 Energy conversion film 2 Resin film (core layer)
DESCRIPTION OF SYMBOLS 3 Front skin layer 4 Back skin layer 5 Energy conversion element 6 Front electrode 7 Back electrode 10 DC high voltage power supply 11 Needle electrode 12 Ground electrode 13 Resin film or resin film provided with electrode 14 Glass plate 15 Insulating sheet 16 Iron ball 17 Lead wire 18 Lead wire 19 High-speed recorder 20 Sample (energy conversion element)

Claims

An energy conversion film comprising at least a charged resin film made of a resin film containing at least a thermoplastic resin and a metal soap;
An energy conversion element comprising: an electrode provided on at least one surface of the energy conversion film.
2. The energy conversion element according to claim 1, wherein the thermoplastic resin includes a polyolefin-based resin, and the metal soap has a melting point of 50 ° C. to 220 ° C.
The energy conversion element according to claim 1 or 2, wherein the metal soap is a salt of a fatty acid having 5 to 30 carbon atoms and a metal.
4. The energy conversion element according to claim 1, wherein the metal soap is a salt of a fatty acid and a metal belonging to Group 2 to Group 13 of the periodic table.
The energy conversion element according to claim 3 or 4, wherein the metal is at least one of zinc, calcium, and aluminum.
The energy conversion element according to any one of claims 1 to 5, wherein the resin film is a porous resin film having pores therein.
The energy conversion element according to any one of claims 1 to 6, wherein the energy conversion film includes at least a charged resin film in which charges are injected into the resin film by a direct current corona discharge treatment.
8. The energy conversion element according to claim 1, wherein the electrode has a surface resistivity of 1 × 10 −3 Ω / □ to 9 × 10 7 Ω / □.
The energy conversion element was heat-treated at 85 ° C. for 14 days, and then left standing on a horizontal surface at a temperature of 23 ° C. and a relative humidity of 50%, and a height of 9.5 mm and a mass of 3 mm from a height of 8 mm in the vertical direction. The energy conversion element according to any one of claims 1 to 8, wherein a maximum voltage generated by an impact when a 5 g iron ball is naturally dropped is 5 mV or more.
It is characterized by comprising at least a charged resin film made of a resin film containing at least a thermoplastic resin and a metal soap,
Energy conversion film.